where C ¼ εS/d is the capacitance of a parallel plate capacitor of plate area S and distance d between the plates. This result is
identical to that in Method (1).
Here, we have an example in which the displacement current is actually necessary to account for the behavior of the
circuit. In its absence, we must assume that current cannot flow through the capacitor. In circuit theory, displacement
currents are not normally used or assumed. To account for their effects, the common explanation is that the plates of the
capacitor are alternately charged with positive and negative charges.